Gate for free spillway weirs

ABSTRACT

A gate is provided with a barrier capable of retaining water with a central barrier wall that is inclined in a direction away from the water, a bottom structure beneath the water that is capable of delimiting by a weir a bottom chamber filled with air and holding the barrier in its water retaining position by the water pressure exercised on said bottom structure, and an inlet extending beyond the retaining level of the barrier with an upper opening that allows water to flood the bottom chamber so as to offset the water pressure on the bottom structure and thereby allow a tipping of the gate, wherein a wall structure forms a wall chamber on the central barrier wall, wherein the wall chamber is capable of being flooded so as to assist the tipping of the gate.

TECHNICAL FIELD

The invention relates to a gate for free spillway weirs according to thepreamble of claim 1.

BACKGROUND ART

Excluding means involving a major risk such as sandbags, flashboards andfuse plugs, the current practice when designing overspill dams is suchthat the designer has to choose between free, gated and fuse gatedspillways.

Free spillways are extremely reliable but do not allow operating dams totheir full storage capacity.

Gated spillways, such as conventional and inflatable gates, allowoperating dams to their full storage capacity but are not fullyreliable, because 30% of gate dam failures are due to a malfunctioningof gates.

A particular type of floodgates is known as fusegates, which arearranged side-by-side on a weir to form a watertight barrier in order tostore water. In case of huge floods, they are configured toautomatically tip and be washed away in order to protect the dam frombeing overtopped and/or to prevent the flooding of the reservoir banks.Typically, each gate is configured to tip at a predetermined floodlevel, so that multiple gates can be configured to gradually open as theflood level is rising.

Therefore, fusegate spillways are the preferred choice when theprobability of an overturning of the gate is low. However, it isparticularly desirable to reduce the effect of abnormal loads, such asfloating debris, or external parameters, such as civil engineeringspillway tolerances, on the reliability of the gate. It is alsoparticularly desirable to be in a position to precisely set the gatestability.

U.S. Pat. No. 5,032,038 (A) discloses a fusegate on the sill of aspillway comprising at least one heavy element, said fusegate beingcapable of resisting the water loads when spilling moderate heads (fordischarging the floods of shorter recurrence intervals) by virtue oftheir own weight but breaching by overturning at a predetermined headcorresponding to a level not higher than a predetermined maximum waterlevel in order to discharge larger floods.

EXTENDED DESCRIPTION OF THE INVENTION

The problem solved by the present invention is to further develop a gatefor free spillway weirs according to the preamble of claim 1, so thatthe gate is improved with respect to its stability.

This problem is solved by a gate for free spillway weirs comprising thefeatures of claim 1. Preferable embodiments are set forth in thedependent claims.

The gate for free spillway weirs according to the invention comprises abarrier capable of retaining a body of water at a predeterminedretaining level with a central barrier wall that is inclined in adirection away from the body of water, a bottom structure beneath thebody of water that is capable of delimiting by a weir a bottom chamberfilled with air and holding the barrier in its water retaining positionby the water pressure exercised on said bottom structure, and an inletextending beyond the retaining level of the barrier with an upperopening beneath a predetermined flood level that allows water to floodthe bottom chamber so as to offset the water pressure on the bottomstructure and thereby allow a tipping of the gate, wherein a wallstructure forms a wall chamber on the central barrier wall, wherein thewall chamber is capable of being flooded so as to assist the tipping ofthe gate. Compared to conventional fusegates, such a gate is more stableat all water levels, because it requires the additional overturningmoment of the water inside the wall chamber. Therefore, the gate is lesslikely to accidently tip when heavy objects, e.g. tree trunks, travelingwith the current at flood levels between the retaining and the floodlevel hit the gate.

It is particularly advantageous that the wall chamber of the gate iscapable of being flooded in association with the bottom chamber. Thus,the additional overturning moment on the central barrier wall due to thewater flooding the wall chamber can be controlled.

Preferably, the gate is capable of tipping when flood water has filledthe wall chamber to at least a predetermined level. Depending on thepredetermined level, the quantity of water inside the wall chambernecessary for the gate to tip can be set. The higher the quantity ofwater required is, the more stable the gate is up to the flood level,whereas the lower the quantity of water required is, the faster and morereliably the gate turns.

Further advantageous is that the inlet of the gate is capable of fillingthe wall chamber and then the bottom chamber. In this way, the necessaryadditional overturning moment of the water inside the wall chamber isachieved before the bottom chamber is filled, which leads to a fastertipping of the gate once the bottom chamber is filled.

It is particularly advantageous that a partitioning structure of thegate divides the space within the wall structure into the wall chamberand flow-through means leading to the bottom chamber. The main reasonfor this is to improve the compactness of the gate and integrate thisnecessary component together with the wall chamber into one easilysealable wall structure.

Preferably, the partitioning structure is a partitioning wall extendingupwards inside the wall structure. Such a partitioning wall issufficient to efficiently delimit a wall chamber inside the wallstructure.

Further advantageous is that the wall structure extends from the top ofthe central barrier wall in a direction towards the bottom chamber.Since the top of the inclined central barrier wall is farthest from thetipping axis of the gate, it is desirable to increase the lever of theflooded wall chamber by placing it at the top of the central barrierwall in order to maximize the achievable overturning moment.

It is further advantageous that the wall structure extends substantiallyalong the entire central barrier wall. Thus, the capacity of the wallchamber can be further maximized, which results in a greater additionaloverturning moment.

Preferably, the wall chamber extends substantially in parallel to thecentral barrier wall. Thereby, the direction of the hydrostatic force ofthe body of water corresponds to the inclination of a conventional gatewithout the wall chamber.

Further advantageous is that the inlet is integral with the wallstructure. Thereby, the inlet can lead water directly to the wallchamber.

Particularly advantageous is that the wall structure is integral withthe bottom structure. Such an arrangement renders the gate very compactand also offers the possibility to maximize the capacity of the wallchamber in a downward direction.

Preferably, a top plate of the bottom chamber constitutes a bottom ofthe wall chamber. Such a close arrangement of bottom and wall chamberbenefits the compactness of the gate and at the same time maximizes thecapacity of both chambers.

It is further advantageous that the bottom chamber is capable of beingfilled with water from the wall chamber through a hole in the top plate.The positive effect is that external connecting means leading from onechamber to the other are not necessary.

Particularly advantageous is that the wall chamber has a drain hole thatis capable of releasing water in case of rain, spindrift or wave to thebottom chamber or to the outside of the gate away from the body ofwater. Such a drain hole prevents the wall chamber from beingaccidentally filled with water and flooded before the actual floodconditions occur.

It is further advantageous that the bottom chamber has a drain hole thatis capable of releasing water to the outside of the gate away from thebody of water with a significantly lower maximum water throughput thanthe water throughput for flooding the wall chamber and the bottomchamber, and wherein the section of the drain hole of the wall chamberis smaller than the section of the drain hole of the bottom chamber. Theadvantage of this is that such a drain hole is big enough to removewater accidentally entered through the inlet, e.g. rain water, and atthe same time small enough to not affect the functioning of the gate atflood conditions.

Preferably, a ballast block on top of the bottom structure assists theholding of the barrier in its water retaining position. The ballastblock allows the gate to be stably installed on the weir when the bodyof water is still absent. Also, such ballast blocks can be easily madein different sizes, materials and weights such that each gate dependingon the flood level at which it is intended to tip can be balancedprecisely by a balance block while the more complex structures of thegate, e.g. the bottom structure, remain basically unchanged.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an embodiment of the gate in a perspective view.

DESCRIPTION OF THE EMBODIMENT

FIG. 1 shows a steel gate 1 on a flat free spillway weir 2 in anupright, water retaining position. The gate 1 has, as a main component,a barrier 3 with an U-shape being open towards a body of water W andextending upwards to a predetermined retaining level RL. The barrier 3is formed by a central barrier wall 4 that is inclined in a directionaway from the body of water W and two side barrier walls 5, 6 that areperpendicular to the weir 2. Toe abutments 100 are fixedly connected tothe weir 2 and abut against the central barrier wall 4 on its sidefacing away from the body of water W.

A bottom structure 7 is located within the barrier 3 at a lower portionof the gate 1 and close to the weir 2. The bottom structure 7 has: a topplate 9 that extends in parallel to the weir 2 and along the barrier 3;and a back plate 10 that extends from the free end of the top plate 9along the free ends of the side barrier walls 5, 6 to the weir 2. Aballast block 11 is placed on top of the top plate 9 at its free end.The bottom structure 7 is watertightly welded to the barrier 3 such thatit delimits a bottom chamber 8 by the weir 2 and the barrier 3. Thebottom chamber 8 has two holes 20, 22: a drain hole 22 cut out in thebottom of the central barrier wall 4; and a hole 20 in the top plate 9close to the central barrier wall 4.

A wall structure 12 extends from the top plate 9 of the bottom structurealong the central barrier wall 4. The wall structure 12 has: a wallplate 15 that extends from the top plate 9 upwards between the sidebarrier walls 5, 6 and substantially in parallel to and along the entirecentral barrier wall 4 to the top edge of the central barrier wall 4;and a partitioning wall 16 that extends from the top plate 9 upwardsbetween the central barrier wall 4 and the wall plate 15 and in parallelto the side barrier walls 5, 6 to a predetermined height. The wallstructure 12 is watertightly welded to the top plate 9, the side barrierwalls 5, 6 and the upper edge of the central barrier wall 4. Thepartitioning wall 16 is displaced towards the one side barrier wall 5and divides the space inside the wall structure 12 into a bigger wallchamber 13 and a smaller flow-through shaft 14. The wall chamber 13 andthe flow-through shaft 14 are connected through a bigger opening betweenthe upper edge of the partitioning wall 16 and the wall plate 15 and asmaller drain hole 21 cut-out in the bottom of the partitioning wall 16.The hole 20 in the top plate 9 leads to the flow-through shaft 14 andthereby connects the wall chamber 13 and the bottom chamber 8.

An inlet 17 extends upwards from the top of the wall structure 12 andsymmetrically to the side barrier walls 5, 6. The inlet 17 is welded tothe wall plate 15 and has an upper opening 18 beneath a predeterminedflood level FL and a lower opening 19 leading through the wall plate 15to the wall chamber 13.

The operation of the gate of the first embodiment is as follows:

When the level of the body of water W is below a flood level FL, thegate 1 shown in FIG. 1 is in the upright position. In this position, thewater pressure of the body of water W exercised on the bottom structure7 is enough to press the bottom structure 7 against the weir 2 andthereby hold the gate 1 in its upright position. As soon as the body ofwater has reached the predetermined flood level FL, water enters throughthe upper opening 18 of the inlet 17 and fills through the lower opening19 of the inlet 17 the wall chamber 13. When the water inside the wallchamber 13 has reached the predetermined height of the partitioning wall16, it overflows the upper edge of the partitioning wall 16 and flowsthrough the flow-through shaft 14 and the hole 20 in the top plate 9into the bottom chamber 8. As the bottom chamber 8 is filled, the waterpressure on the bottom structure 7 holding the gate 1 is being offset.Thus, the hydrostatic pressure of the body of water W acting on the wallplate 15 and the additional overturning moment of the filled wallchamber 13 cause the gate 1 to tip over the toe abutments 100.

1. A gate for free spillway weirs, comprising: a barrier capable ofretaining a body of water at a predetermined retaining level with acentral barrier wall that is inclined in a direction away from the bodyof water; a bottom structure beneath the body of water that is capableof delimiting by a weir a bottom chamber filled with air and holding thebarrier in its water retaining position by the water pressure exercisedon said bottom structure; and an inlet extending beyond the retaininglevel of the barrier with an upper opening beneath a predetermined floodlevel that allows water to flood the bottom chamber so as to offset thewater pressure on the bottom structure and thereby allow a tipping ofthe gate; a and a wall structure forming a wall chamber on the centralbarrier wall, wherein the wall chamber is capable of being flooded so asto assist the tipping of the gate wherein the inlet is integral with thewall structure and leading directly to the wall chamber.
 2. A gateaccording to claim 1, wherein the wall chamber is capable of beingflooded in association with the bottom chamber.
 3. A gate according toclaim 1, wherein the gate is capable of tipping when flood water hasfilled the wall chamber to at least a predetermined level.
 4. A gateaccording to claim 1, wherein the inlet is capable of filling the wallchamber and then the bottom chamber.
 5. A gate according to claim 1,wherein a partitioning structure divides the space within the wallstructure into the wall chamber and flow-through means leading to thebottom chamber.
 6. A gate according to claim 5, wherein the partitioningstructure is a partitioning wall extending upwards inside the wallstructure.
 7. A gate according to claim 1, wherein the wall structureextends from the top of the central barrier wall in a direction towardsthe bottom chamber.
 8. A gate according to claim 1, wherein the wallstructure extends substantially along the entire central barrier wall.9. A gate according to claim 1, wherein the wall chamber extendssubstantially in parallel to the central barrier wall.
 10. A gateaccording to claim 1, wherein the inlet is integral with the wallstructure.
 11. A gate according to claim 1, wherein the wall structureis integral with the bottom structure.
 12. A gate according to claim 11,wherein a top plate of the bottom chamber constitutes a bottom of thewall chamber.
 13. A gate according to claim 12, wherein the bottomchamber is capable of being filled with water from the wall chamberthrough a hole in the top plate.
 14. A gate according to claim 1,wherein the wall chamber has a drain hole that is capable of releasingwater in case of rain, spindrift or wave.
 15. A gate according to claim14, wherein the bottom chamber has a drain hole that is capable ofreleasing water to the outside of the gate away from the body of waterwith a significantly lower maximum water throughput than the waterthroughput for flooding the wall chamber and the bottom chamber, andwherein the section of the drain hole of the wall chamber is smallerthan the section of the drain hole of the bottom chamber.